"Markers" of Alzheimers Do Not Doom You to Dementia

TUESDAY, May 29, 2018 (HealthDay News) -- Even if you discover that you have the first biological signs of Alzheimers, you are not doomed to develop the crippling dementia, a new study suggests.

"Just because you have amyloid [proteins] in the brain does not mean you are going to get dementia tomorrow. It does not mean you are going to get dementia in five years," said lead researcher Ron Brookmeyer. He is a professor of biostatistics with UCLA Fielding School of Public Health.

"It could be many years, and it could be longer than your natural life expectancy," Brookmeyer added.

For example, high levels of abnormal amyloid proteins in your brain or shrinkage of your brain each confer only a minimal risk of future dementia, a new statistical risk model indicates.

Further, dementia risk is even lower if the amyloid or shrinkage is detected at a more advanced age, the study authors noted.

On the other hand, risk does rise if early biological signs of Alzheimers start stacking up, the investigators found.

For instance, a 60-year-old man with high levels of amyloid protein has just a 23 percent chance of developing dementia in his lifetime, while a 60-year-old woman has a 31 percent risk, the researchers said.

Shrinking of specific brain regions confer similarly low lifetime dementia risks at age 60; about 23 percent for men and 30 percent for women.

But if men or women have both high amyloid levels and brain shrinkage at age 60, their dementia risk increases to 34 percent and 42 percent, respectively, according to the report.

People face the most risk if they have high amyloid levels, brain shrinkage and early signs of mild cognitive impairment, the researchers explained. This impairment usually crops up as memory loss.

With all three signs present, 60-year-old men and women have a 93 percent and 96 percent risk of developing Alzheimers, respectively.

Age and life expectancy also play a strong role in Alzheimers dementia risk, Brookmeyer said.

Dementia risk decreases with age because it is less likely a person will develop Alzheimers during their lifetime, he explained. But life expectancy also plays a part.

"Females will generally have higher risks, because females have a longer life expectancy. With a longer life expectancy, there is more time for the preclinical disease to progress," Brookmeyer said.

For this study, the researchers analyzed data on just over 2,000 people who participated in two long-term studies on Alzheimers disease. These studies included scans for amyloid, brain shrinkage and cognitive impairment, all of which can be observed before a person falls victim to dementia.

This study could be considered good news for the 46.7 million Americans who carry some early signals of Alzheimers disease, Brookmeyer said.

"It may actually provide some reassurance to people that despite testing positive on some screening tests, their chances of developing Alzheimers dementia may remain low," Brookmeyer said.

However, he noted that the model needs to be further refined to include other factors -- such as genetics -- that affect dementia risk.

James Hendrix, director of global science initiatives for the Alzheimers Association, agreed that it is too early to take much hope from this study.

"I think we probably do ourselves a little bit of a disservice if we focus so much on the overall conclusion that Alzheimers risk is less than we thought, because I do not think we know that for sure," Hendrix said. "We need to dig into the numbers a little bit more and understand what is happening in the continuum of Alzheimers disease as it progresses."

Hendrix is particularly concerned that these findings might prompt complacency in people, making them "think this is a solved problem."

As a result, people might slack on advocacy, volunteer efforts in their community, or volunteering for clinical trials that are critical to understand Alzheimers, he said.

"The problem is not diminished," Hendrix said. "It is still there, and we need people to remain engaged."